Food preferences and activity habits set in early childhood can profoundly influence lifelong trajectories for Body l\/lass Index (BMI) and health. Specifically, rapid BMI gain in early childhood has been established to affect adulthood mortality and morbidity. Unfortunately, the longer such unhealthy patterns are in place, the more difficult it can be to reverse them. Therefore, healthy lifestyle interventions targeted at children as early as preschool 'have enormous potential to affect lifelong health. Furthermore, nutrition and activity patterns are determined not only at the child level, but within the family and the community. Building on the success of an existing partnership between Vanderbilt Pediatrics and Metro Parks and Recreation in Nashville, TN, we will conduct and evaluate an intervention intended to prevent obesity in preschoolers in an approach that affects multiple levels of risk and is both family-based and community centered. Prior to launching a large randomized controlled trial (RCT), formative research (focus groups and pilot studies) will be conducted to refine the intervention components. In the RCT, 600 parent-preschool children dyads from low income neighborhoods will be randomly assigned to one of two conditions. In the intervention condition, groups of parent-child dyads will participate in an empirically tested, literacy-sensitive, skills building curriculum to improve: 1) caloric intake with appropriate macronutrients, and 2) routine physical activity for both parent and child. The intervention condition will occur in community centers and utilize tools including goal setting, self-monitoring, and problem solving. In the control condition parent-child dyad groups will receive a literacy promotion/school success curriculum. Both conditions will have 90-minute sessions in: 1) an initiation phase (weekly for 3 months); 2) a maintenance phase (biweekly for 6 months); and 3) a sustainability phase (monthly for 27 months). The primary outcome of interest will be early childhood BMI trajectories measured at multiple time points over the three year RCT. Additional measures collected throughout the study from children and parents will include: bioelectrical impedance; waist circumference; actigraphy; 3-day diet recalls; questionnaires; social network data; and saliva to assess a genetic risk score associated with obesity. RELEVANCE: Pediatric obesity prevention must occur in preschool given that 60% of oven/weight preschoolers will go on to become overweight adolescents. By conducting and testing trials in public community centers, exportable interventions could result allowing for a macro-level system change to address this expanding public health crisis.